1. Field of the Invention
The present invention relates to method and apparatus of producing a tobacco smoke filter having a double structure composed of an inner core phase in a special fibrous arrangement and an outer skin layer in a different fibrous arrangement therefrom, surrounding the core phase. The tobacco smoke filters according to the present invention possess high collapse strengths and physical and chemical characteristics in which the filtration efficiency of tastable component is low whereas the filtration efficiencies of tar and total particlate matter hereinafter referred to as the "TPM" when applicable, which are components harmful on health, contained in tobacco smoke are high. Further, the tobacco smoke filter according to the present invention allows a small amount of bundle of filaments to be used for producing a tobacco smoke filter without a decrease in filtration efficiency thereof.
2. Description of the Prior Art
It is well known, for example, in Japanese Patent Publication No. 39/28539 and unexamined published Japanese Patent Application No. 53/47599, that tobacco smoke filter are so constructed that the fibers are folded in the transversal direction as shown in FIG. 3. In smoke filters in such a fibrous arrangement, when the fibers are wound into filter plugs, the fibrous arrangement or structure tends to be misaligned, and it is, therefore, impossible to effectively produce tobacco smoke filters having uniform fibrous fillings and stable configurations. Such a filter tends to bend and is held in smoker's mouth resulting in deformation.
On the other hand, various methods of producing tobacco smoke filters, in which an air jet is used as means for supplying fiber's tow to a plug machine are disclosed, for example, in U.S. Pat. Nos. 3,016,945 and 3,050,430. It is the feature of these tobacco smoke filter producing methods that a tip end of the air jet means is disposed adjacent an end of a tongue, and the filament tow is fed to thereby produce plain filters so as to maintain the crimps formed on a number of filaments of the tow. It is impossible to uniformly fold the fiber's tow in the transversal or crosswise direction to the filter axis by overfeeding the tow from such an air jet into the inner space in the tongue. Therefore, there has been a strong demand for improvements to the coupling manner between the air jet and the tongue of the filter forming machine and to structures of the air jet and the tongue in order to produce a tobacco smoke filter having a specific fibrous arrangement structure and skin core type structure as defined by the present invention.